1. Field of the Invention
The present invention relates to an optical cable that can be divided later with improved ease.
2. Background Art
An optical cable having a structure like that shown in FIG. 9 has been proposed recently.
In FIG. 9, numeral 1 indicates an optical ribbon core laminate in which multiple layers of optical fiber ribbon have been laminated together. This optical ribbon core laminate 1 is not fixed completely in place inside of the forming pipe 2, but rather is housed with an interval of spacing between itself and forming pipe 2.
This forming pipe 2 is formed into the shape of a pipe by employing a pipe forming method in which tape, consisting of a rigid plastic film like polyester, polypropylene, polyethylene, polyamide, or fiber reinforced plastic (FRP), is continuously fashioned into a pipe shape. The seams running along the longitudinal direction of this forming pipe 2 are then joined together by meaning of adhesive tape 3.
The forming pipe 2 is covered with a sheath 4 consisting of polyethylene or plasticizing polyvinyl chloride or the like. The formation of sheath 4 is carried out using the usual extruding and cladding method. In addition, two tension members 5, consisting of fiber-reinforced plastic or steel, brass or other such metal wire, and two rip cords 6, consisting of plastic cords, are embedded in the sheath 4. The tension members 5 are disposed opposite one another with the optical ribbon core laminate 1 interposed between them. Rip cords 6 are disposed opposite one another with the optical ribbon core laminate 1 interposed between them, and so as to be perpendicular to a line joining the two tension members 5.
In order to support and house the optical ribbon core laminate 1 within the forming pipe 2 without completely fixing it in place, an intermittent filling material (not shown) consisting of a soft hot-melt adhesive is employed to fill the optical cable at intermittent points along the longitudinal direction thereof.
When subsequently dividing an optical cable of this design, the sheath 4 is cut open by pulling both rip cords 6, thereby dividing the optical cable into two parts. However, it can be difficult to divide the forming pipe 2 due to its high resistance to tearing, or because it adheres to the sheath 4, for example. Thus, it can take some time to expose the optical ribbon core laminate 1 inside. In other words, this optical cable does not always demonstrate excellent subsequent dividing.
The present invention has as its objective to improve the ease with which an optical cable of the above-described design can be divided later.
This objective is achieved in an optical cable of the above design by enabling a forming pipe fashioned from a plurality of tape to be divided along its longitudinal direction.
In this case, it is preferable to provide rip cords near the seams of this forming pipe.
More preferably, indicators showing the position of the rip cord are formed to the outer periphery of the sheath provided around the forming pipe. These indicators are preferably projections, grooves or an indicator formed by printing or extrusion.
It is also preferable that the forming pipe be filled with hot-melt resin intermittently along its longitudinal direction.
Alternatively, it is desirable to provide a shock-absorbing material to the inner surface of the forming pipe. This shock-absorbing material is preferably one in which a non-woven fabric is adhered to the resin film, and a water absorbing powder is affixed to this non-woven cloth.